S-52, S-57, S-63 and S-101

The International Hydrographic Organization (IHO) has published a number of publications that standardize how electronic navigational charts (ENC) data should be encoded, visualized and protected:

  • S-57 (IHO Transfer Standard for Digital Hydrographic Data) is the standard used for the exchange of digital hydrographic data between national hydrographic offices and for its distribution to manufacturers, mariners and other data users. It defines how ENC cell data should be physically encoded to files.

    The S-57 implementation is based upon the IHO Transfer Standard for Digital Hydrographic Data - Special Publication No. 57 - Edition 3.1 - November 2000.

  • S-52 (Specifications for Chart Content and Display Aspects of ECDIS) specifies how ENCs should be visualized on a map. It provides a symbology set and a number of rules that rigorously define how each individual object in an ENC cell should be displayed, by specifying the symbol, color and line style.

    The S-52 implementation is based upon the Specifications for Chart Content and Display Aspects of ECDIS - Special Publication No. 52, and the IHO Presentation Library User’s Manual - Edition 4.0(.4) - October 2024.

    Parts of the S-52 specification are not freely available, but need to be purchased via the IHO office.

  • S-63 (IHO Data Protection Scheme) provides a mechanism to encrypt and protect ENC data from unauthorized use.

  • S-101 (IHO’s modern ENC data model and specification) defines the content, structure, and metadata required to produce a fully compliant S‑101 ENC and to support its portrayal within any S‑100 based system built on the S‑100 Universal Hydrographic Data Model. S-101 defines symbology through a modular, machine-readable component called the Portrayal Catalogue. The Portrayal Catalogue contains all the graphic primitives needed for display, including symbols, pixmaps, complex line styles, area fills, fonts, and colour profiles. See Comparing S-57 and S-101: key updates and improvements for more information about the distinction between S-57 and S-101.

These publications can be downloaded from the IHO website at the following location: http://www.iho.int/iho_pubs/IHO_Download.htm

AML and IENC

Although S-57 was initially designed for the encoding of ENC data, the standard can also be used for the encoding of other products. One such product is Additional Military Layers (AML), which is used for the encoding of military nautical data. Another is InlandECDIS (IENC), used for river navigation.

AML

The AML feature and attribute resources are based upon the AML Feature and Attribute Catalogue version 3.0.1.

The visualization of AML is based on the AML Portrayal Specification version 3.0.0.

Reference information on AML, including the Feature and Attribute Catalogue, can be downloaded at the following location: http://www.ukho.gov.uk/Defence/AML/Pages/Home.aspx

IENC

The IENC feature and attribute resources, as well as the visualization rules, are based on the InlandECDIS specification version 2.4. You can use it to open IENC versions 2.0, 2.1, 2.2, 2.3 and 2.4.

Comparing S-57 and S-101: key updates and improvements

S-101 introduces several enhancements over S-57, aimed at improving the usability and functionality of electronic navigational charts in modern ECDIS systems. Key updates and improvements include:

  • Alignment with ISO 19100 standards: S-101 is developed in line with modern geospatial standards, enabling more dynamic and interoperable data display in ECDIS.

  • Improved mariner experience: S-101 supports a fully machine-readable catalogue system, reducing the need for manual ECDIS upgrades.

  • Easier updating: S-101 allows ENC producers to highlight added, deleted, or modified features in updates, streamlining route planning for mariners.

  • Complex attributes and geometries: S-101 introduces enhanced attributes and composite curves for more realistic chart presentations.

  • Data protection: S-101 provides an encryption scheme to protect data from unauthorized access. The scheme is conceptually similar to S-63, but uses more modern cryptographic standards.